1. Field of the Invention
The present invention relates to a luminance compensation device, and more particularly, to a luminance compensation device utilizing a photosensitive technology to compensate for the luminance of a backlight module.
2. Description of Related Art
As technology advances, liquid crystal displays (LCDs) are becoming more and more popular. However, LCDs age over a period of time, especially the backlight module of a LCD. In some backlight modules, the primary light source used consists of light emitting diodes (LEDs). The light intensity of the light emitted by LEDs varies according to the device temperature and the degree of aging of the device. Since the backlight module ages over time, in order for a liquid crystal display to display consistent luminance and colors, the luminance and the colors of the backlight module need to be compensated.
FIG. 1 is a schematic view illustrating a conventional luminance compensation device for a backlight module. Please refer to FIG. 1. The backlight module includes a power converter 10, a backlight driving unit 20, a light emitting diode 30, a light sensor unit 40 and a control unit 50. Herein, the power supply converter 10 is used to provide the voltage required by the backlight driving unit 20. The backlight driving unit 20 is used to provide the voltage and the current required by the light emitting diode 30. The light emitting diode 30 generates corresponding light intensity according to the voltage and the current provided. Next, the light sensor unit 40 is used to sense the light intensity of the light emitted by the light emitting diode 30 and transmits a detection signal to the control unit 50. The control unit 50 adjusts the backlight driving unit 20 according to the detection signal in order to adjust the light emitting diode 30 by feedback control. Hence, luminance compensation for the backlight module is achieved.
Further, U.S. Pat. Nos. 6,127,783, 6,344,641, 6,441,558, 6,448,550, 6,495,964, and 6,894,442 also disclose a similar method as described above. It should be noted that the differences among U.S. Pat. Nos. 6,127,783, 6,344,641, 6,441,558, 6,448,550, 6,495,964, and 6,894,442 include the driving timing, the location where the light sensor unit 40 is disposed, and the type of light sensor unit used. Also, the method disclosed by U.S. Pat. Nos. 6,127,783, 6,344,641, 6,441,558, 6,448,550, 6,495,964, 6,894,442 utilizes the control unit 50 to control the light intensity of the light emitting diode 30 based on the light intensity sensed by the light sensor unit 40. Yet, additional costs are required to manufacture the control unit 50 and the adjustment that can be made to the light intensity of the light emitting diode 30 is rather limited.
Therefore, LCD manufacturers have been looking for suitable solutions to overcome the aforementioned problems.